Pitch change mechanism including improved electro-hydraulic actuators

Abstract

The invention relates to a pitch change mechanism for a turbopropeller (10), comprising: - an electric motor (29) fixedly mounted on a stator portion of the turbopropeller and comprising an actuation shaft (21); - an axial piston hydraulic pump (20) suitable for pressurizing a hydraulic fluid, the hydraulic pump comprising: a body (22) driven by the propeller (10); a barrel (23) containing a set of pistons (24), each comprising a sliding pad (25); and a disc (26) inclined with respect to the rotation axis, each sliding pad being supported on the disc, the disc (26) being fixedly connected to the stator portion of the turbopropeller with one of the barrel (23), the disc (26) being fixed to the actuation shaft (21) for co-rotation with the other of the barrel (23).

Description

Technical Field

[0001] This invention relates to the field of turbines, including propellers or variable-pitch fans. More specifically, this invention relates to a system for actuating the pitch of the propeller or fan of such a turbine. Background Technology

[0002] Different turbine designs seek propellers (turboprops, open rotors) or fans (turbojet engines) with variable pitch. This variability allows the turbine to adapt to varying flight conditions by maintaining a favorable angle of incidence of air on the blades. Variable pitch is particularly necessary for rotors with low compression ratios, such as fans of turbines and propellers of turboprops, which have high expansion ratios (the ratio of the flow rate of the secondary (cooled) flow to the flow rate of the main (through-body) flow).

[0003] Numerous pitch-changing mechanisms have been envisioned to alter the pitch of propeller or fan blades. These mechanisms typically involve a setup that rotates the blades about their main axis via a rod actuated by an actuator. The actuator is supplied with hydraulic fluid (e.g., oil) from the turbine's lubrication unit, and changes in the pressure of the delivered hydraulic fluid alter the pitch. To transfer the hydraulic fluid supply of the pitch-changing mechanism from the turbine's stationary reference frame (lubrication unit) to the rotating reference frame (fan), an oil transfer bearing (OTB) is typically used. In a manner known per se, the OTB comprises a stationary section fixed relative to the turbine's stator and connected via a dedicated channel to the lubrication unit, which includes an oil tank and pump. The rotating section moves as a unit with the turbine's rotor. However, the OTB is a complex and fragile device, prone to failure, particularly severe oil leaks, which can affect turbine reliability. It also requires the installation of a return oil pump and an oversized oil tank, which can cause supply problems during some maneuvers. Furthermore, this configuration is limited when operating at low ratings because it relies on the high-pressure body rating of the turbine. Finally, this configuration requires blade pitch locks (“pitch locks”), which are heavy, complex, expensive, and prone to locking.

[0004] Furthermore, since the start-up of the lubrication unit is usually related to the start-up of the turbine, it is necessary to provide auxiliary systems to offer some protective functions, especially in the event of overspeed or engine shutdown. Therefore, it is necessary to provide a feathering system that can operate even without hydraulic fluid pressure.

[0005] In addition, the pitch changing mechanism must be able to ensure that it retracts from the feathering position when the engine is stopped. Summary of the Invention

[0006] One object of the present invention is to provide a variable pitch turbine that overcomes the disadvantages of the prior art mentioned below.

[0007] Another object of the present invention is to provide an independent pitch changing mechanism that eliminates the difficulties associated with the delivery of hydraulic fluid from a fixed reference frame to a rotating reference frame.

[0008] Another object of the present invention is to provide a pitch changing mechanism that can be used regardless of the turbine's operating state, and which can ensure the protection and feathering functions of the turbine's propeller / fan blades, preferably without relying on the electrical control system.

[0009] Another object of the present invention is to provide a pitch changing mechanism that can be implemented in an open rotor type turbine including a propeller or a turboprop type turbine, and in a turbojet engine including a fan.

[0010] Therefore, according to a first aspect, the present invention provides a pitch changing mechanism for a turbine propeller, the turbine including a stator and a rotor, the pitch changing mechanism including an electro-hydraulic actuator, the pitch changing mechanism comprising:

[0011] - An electric motor, which is fixedly mounted on the stator portion of the turbine and includes an actuation shaft capable of rotating about a rotational axis;

[0012] - Axial piston hydraulic pump, suitable for pressurizing hydraulic fluid, the hydraulic pump includes:

[0013] The main body is driven by a propeller;

[0014] The cylindrical section houses a set of pistons circumferentially distributed around the axis of rotation, each piston including a sliding pad; and

[0015] The disk is tilted relative to the axis of rotation, and each sliding pad is supported on the disk.

[0016] One of the swash plate and the cylinder is fixedly connected to the stator of the turbine to prevent the swash plate and the cylinder from rotating about the actuation shaft, while the other of the swash plate and the cylinder is rotatably fixed to the actuation shaft.

[0017] Advantageously, the invention is achieved by the following features, which are employed individually or in any combination of technically possible combinations of these features:

[0018] -The motor is an asynchronous motor;

[0019] - The swash plate is fixedly connected to the stator section of the turbine, and the mechanism also includes a first bearing configured to support the actuation shaft and a second bearing configured to support the swash plate;

[0020] -The first bearing is installed between the actuation shaft and the disc;

[0021] -The second bearing is installed between the disc and the main body;

[0022] The disk includes a first part and a second part. The first part includes a surface that is inclined relative to the axis of rotation, so that a sliding pad is supported on the surface. The second part is configured to be attached to the stator part of the turbine.

[0023] - The cylinder is fixedly connected to the stator portion of the turbine, and the mechanism also includes a first bearing configured to support a disc and a second bearing configured to support the cylinder.

[0024] -The first bearing is installed between the disc and the cylinder;

[0025] -The second bearing is installed between the cylindrical section and the main body;

[0026] - The turbine also includes a planetary mechanical reducer, which includes a sun gear, a ring gear, and a planetary gear train. The ring gear is coaxial with the sun gear and is configured to drive the propeller in a rotating manner. The planetary gear train is distributed circumferentially around the axis of rotation of the reducer between the sun gear and the ring gear. Each planetary gear is mounted on a planet carrier fixed relative to the stator of the turbine.

[0027] - Components fixedly connected to the stator section of the turbine in the disc and cylinder are mounted on the planetary carrier;

[0028] - The propeller pitch is controlled by the motor torque control;

[0029] - The pitch changing mechanism also includes a hydraulic fluid reservoir that is rotatably fixed to the propeller;

[0030] - The main body defines the cavity filled with hydraulic fluid, and the pitch changing mechanism also includes:

[0031] o. The cylindrical section is housed within the cavity of the main body to be immersed in hydraulic fluid;

[0032] A set of cylinders formed inside the cylindrical section, each cylinder housing a piston capable of translational movement within the cylinder and including a feed port and a discharge port, the feed port being configured to receive hydraulic fluid from a cavity, and the discharge port being configured to deliver the hydraulic fluid to the actuator of the propeller; and

[0033] o Annular groove, the annular groove is formed in the body and is in fluid communication with the discharge hole;

[0034] - Each cylinder also includes a drain valve, which is mounted on a drain port and configured to prevent hydraulic fluid from flowing in the direction of the cylinder through the annular groove;

[0035] - The exhaust valve is installed in the cylinder;

[0036] - Each cylinder also includes a feed valve, which is mounted on the feed port and configured to prevent the flow of hydraulic fluid in the cylinder along the direction of the cavity;

[0037] - The feed valve is installed near the sliding pad;

[0038] - The feed valve is installed in the cylinder;

[0039] The propeller actuator includes two chambers, and the mechanism also includes a hydraulic valve configured to selectively connect one of the actuator chambers to an annular groove. Attached Figure Description

[0040] Other features and advantages of the invention will become apparent from the following description of preferred embodiments. This description will be given with reference to the accompanying drawings, in which:

[0041] Figure 1 This is a schematic cross-sectional view of an example turbine, which includes a fan or propeller with variable pitch and a pitch changing mechanism according to an embodiment of the invention.

[0042] Figure 2 This is a partial schematic cross-sectional view of an exemplary embodiment of a planetary mechanical reducer, which can be used in a turbine including a pitch changing mechanism according to an embodiment of the present invention;

[0043] Figure 3 This is a schematic cross-sectional view of an example turbine, which includes a fan or propeller with variable pitch and a pitch changing mechanism according to an embodiment of the invention.

[0044] Figure 4 This is a schematic diagram of the propeller pitch changing mechanism according to a variant embodiment;

[0045] Figure 5 This is a schematic diagram of an example of an annular groove formed in the body of the pump;

[0046] Figure 6 This is a schematic diagram of the propeller pitch changing mechanism according to a variant embodiment;

[0047] Figure 7 This is a schematic diagram of a propeller pitch changing mechanism according to a variant embodiment. Detailed Implementation

[0048] This invention is applicable to any turbine with variable pitch, which includes a pitch-changing mechanism. In particular, this invention relates to... Figure 1 The illustrations include turbines with propellers (e.g., turboprops) or other open rotors (ductless propellers) and ducted turbojet engines including fans, wherein the pitch of the fan or propeller blades can be varied according to flight conditions. For the remainder of this application, for the sake of simplicity in the specification and claims, the term "propeller" will be used to refer to the propeller or fan of the turbojet engine as described above.

[0049] Typically, in addition to the propeller, a turbine also includes a mechanical reduction gear 50, such as... Figure 2 As shown, a mechanical reducer is configured to rotatably drive a propeller. The reducer 50 is housed within the turbine housing. The turbine is configured to be fixedly mounted on the aircraft by suitable attachment means (e.g., pylons). For the remainder of this document, the term "stator portion of the turbine" will refer to any portion of the turbine fixed relative to the housing, which is configured to be connected to a pylon, and "rotor portion of the turbine" will refer to any portion that can move about an axis when the turbine is in operation, and by definition, the rotor portion of the turbine is therefore movably mounted relative to the stator portion. As an example, the stator portion includes the turbine housing, within which means for driving the propeller, etc., are housed. For example, the rotor portion includes a propeller and a drive shaft for the propeller.

[0050] Finally, in this application, upstream and downstream are defined relative to the conventional flow direction of gas in and through the propeller. Furthermore, "axis A" of the hydraulic pump refers to the axis of rotation of the hydraulic pump. The axial direction corresponds to the direction of axis A, and the radial direction is the direction perpendicular to and through the axis. Additionally, the circumferential (or transverse) direction corresponds to the direction perpendicular to axis A and does not cross the axis. Unless otherwise stated, the terms "inner" and "outer" are used with reference to the radial direction, such that the inner portion or inner surface of an element is closer to axis A than the outer portion or outer surface of the same element. Furthermore, when an element does not rotate relative to axis A, the element is considered "in a fixed reference frame," while when an element can be driven to rotate relative to axis A, the element is considered "in a rotating reference frame."

[0051] The reducer 50 is planetary and includes:

[0052] -Sun gear 51, the sun gear is centered on the rotation axis of the reducer and is configured to be rotated by the drive input shaft of the turbine.

[0053] - Ring gear 52, the ring gear being coaxial with the sun gear 51 and configured to drive the propeller shaft about the axis of rotation, and

[0054] - Planetary gear train 53, which is circumferentially distributed around the axis of rotation of the reducer between the sun gear 51 and the ring gear 52. Each planetary gear meshes with the sun gear 51 on the inner side and with the ring gear 52 on the outer side. The planetary gear train 53 is mounted on a planet carrier 54, which is fixed relative to the stator of the turbine.

[0055] In a variant, the reducer 50 can be planetary type, in which case the ring gear 52 is fixedly mounted on the stator of the turbine, and the drive shaft is rotatably driven by the planet carrier 54.

[0056] like Figure 3 As shown, the pitch changing mechanism includes an electro-hydraulic actuator 11 (EHA), a hydraulic pump 20, and a motor 29. The electro-hydraulic actuator is configured to actuate actuator 15, which is mechanically connected to propeller 13 to change the propeller pitch. The hydraulic pump is configured to pressurize a fluid (typically oil).

[0057] The motor 29 is fixedly mounted on the stator portion of the turbine, and the motor includes an actuation shaft 21 that is rotatable about the rotation axis A.

[0058] The hydraulic pump 20 is a fixed displacement axial cylinder pump comprising a main body 22, a set of pistons 24 and a disc 26. The main body is driven to rotate by a propeller 13, and the set of pistons is circumferentially distributed around the axis of rotation A.

[0059] More precisely, body 22 defines cavity 224, in which cylindrical portion 23 is rotatably received. A bore forming a cylinder is formed in cylindrical portion 23, and the cylinder is configured to slidably receive piston 24. The translational axis of piston 24 is generally parallel to the rotation axis A. Cylindrical portion 23 and piston 24 are rotatably fixed to actuation shaft 21. Each piston 24 includes a sliding pad 25 configured to be supported on platform 26. The sliding pad 25 is configured to slide freely along disk 26 while remaining supported on disk (constant contact) regardless of the angular position of piston 24 about rotation axis A.

[0060] The disk 26 is mounted around the actuation shaft 21 and is tilted relative to the rotation axis A.

[0061] In the first embodiment, disk 26 is fixedly connected to the stator portion of the turbine to prevent it from rotating about the axis of rotation A. Therefore, the tilting disk 26 cannot rotate about the axis of rotation A (and is thus in a fixed frame of reference). In this embodiment, disk 26 may be mounted on the planet carrier 54 of the reducer 50. In a variant, when the reducer 50 is a planetary reducer (with a drive shaft driven by the planet carrier 54), disk 26 may be mounted on the ring gear 52—however, note that this configuration is more complex to implement than in the case of a planetary reducer.

[0062] The swashplate 26 specifically includes a first portion 26a and a second portion 26b. The first portion includes a surface inclined relative to the axis of rotation, on which the sliding pad 25 is supported. The second portion is configured to be attached to the stator portion of the turbine (typically the planetary carrier 54). The first portion 26a and the second portion 26b pass through a through-hole 26c, which is configured to receive the actuation shaft 21 of the motor 29. As described above, neither the first portion 26a nor the second portion 26b of the swashplate 26 is attached to the actuation shaft 21. Therefore, the actuation shaft 21 is rotatable relative to these two portions of the swashplate 26.

[0063] For this purpose, the electro-hydraulic actuator 11 includes a first bearing 27a configured to support the actuation shaft 21 and a second bearing 27b configured to support the disc 26. For example, the first bearing 27a may be installed between the actuation shaft 21 and a second portion 26b of the disc 26 (in the inner wall defining the through hole 26c), while the second bearing 27b is installed between the disc 26 and the body 22.

[0064] During operation of the electro-hydraulic actuator 11, the cylinder 23 and piston 24 are driven rotatably by the actuation shaft 21 about the rotation axis A. Since the piston 25 is constantly supported on the disk 26, this rotational motion has the effect of displacing the sliding pad 25 along an axis parallel to the rotation axis A, thereby producing a reciprocating movement. The magnitude of this reciprocating movement is determined by the inclination of the disk 26 relative to the rotation axis A.

[0065] exist Figure 6 In the alternative embodiment shown, the cylinder 23 does not rotate about axis A (and is therefore in a fixed reference frame). For this purpose, the cylinder can be mounted on the planetary carrier 54 of the reducer 50, or, when the reducer 50 is a planetary reducer, the cylinder 23 can be mounted on the ring gear 52. In this embodiment, the swashplate 26 is therefore rotatably driven by the actuation shaft 21 about the rotation axis A to produce the reciprocating movement of the piston. As previously described, the disk 26 therefore includes a first portion 26a and a second portion 26b, the first portion including a surface inclined relative to the rotation axis, on which the sliding pad 25 is supported, and the second portion being configured to attach to the actuation shaft 21.

[0066] To achieve rotational locking of the cylinder portion, the electro-hydraulic actuator 11 includes a first bearing 27c configured to support the disc 26 and a second bearing 27d configured to support the cylinder portion 23. For example, the first bearing 27c may be installed between the disc 26 and the cylinder portion 23, particularly at the portion connecting the cylinder portion to the fixed reference system, while the second bearing 27d is installed between the cylinder portion 23 and the body 22.

[0067] During operation of the electro-hydraulic actuator 11, the disc 26 is driven to rotate about the axis of rotation A by the actuation shaft 21. The cylinder 23 is fixed. Since the piston 25 is constantly supported on the disc 26, this rotational motion has the effect of displacing the sliding pad 25 along an axis parallel to the axis of rotation A, thereby producing a reciprocating movement. The magnitude of this reciprocating movement is determined by the inclination of the disc 26 relative to the axis of rotation A.

[0068] This alternative embodiment makes the operation of the pump strictly similar to the operation of the pump described above.

[0069] Therefore, this structure enables the creation of an electro-hydraulic actuator 11 whose operation is independent of the rotation of the actuator body 22, which is released only when the actuation shaft 21 is driven by the motor 29. However, since the motor 29 is not actuated by the reducer 50, the rotation of the actuation shaft 21 is independent of the turbine's operation. The advantage of this operating mode is that it allows the propeller 13 pitch to be changed even when the turbine is stopped. Therefore, even if the turbine malfunctions during flight, feathering of the propeller 13 can be performed. Furthermore, the propeller 13 pitch can be changed before the turbine starts, thus enabling the function to exit the feathering position. Moreover, since the actuation shaft 21 only needs to be rotated by the motor 29 when there is a command to change the pitch, an excessively large motor 29 is no longer required.

[0070] Furthermore, since the operation of the electro-hydraulic actuator 11 is independent of the rotation of the actuator body 22, the operation of the hydraulic pump 20 can be completely controlled by the motor 29. Therefore, this operating mode allows for easy modification of the generated hydraulic fluid pressure by changing the operating parameters of the motor 29. Specifically, the propeller pitch is directly controlled by the hydraulic pump pressure generated by the hydraulic fluid pump 20, which depends on the displacement speed of the piston 24. The control of the propeller pitch 13 can be achieved using a servo system connected to the motor 29. In this embodiment, the motor 29 is an asynchronous motor, which does not require any resistive torque in the event of a short circuit, thus reducing the risk of fire.

[0071] Furthermore, the pump here has a fixed displacement, which improves the lifespan and robustness of the electro-hydraulic actuator compared to pumps with variable displacement.

[0072] In one embodiment, the electro-hydraulic actuator 11 also includes a hydraulic fluid tank 16 rotatably fixed to the propeller 13. The tank has the function of ensuring minimum pressure at the pump supply section by means of a check valve, and also has the function of preventing any risk of overpressure at the discharge section by means of an overpressure valve in the event of heating.

[0073] The body 22 of the hydraulic pump 20 also includes a discharge port 221 and a feed port 222, which are in fluid communication first with the cylinder of the piston 24 and second with the actuator 15 of the pitch changing mechanism to supply pressurized fluid to the actuator 15. Since the body 22 of the hydraulic pump 20 is rotatably fixed to the propeller 13, the discharge port 221 and feed port 222 can also rotate relative to the piston 24, thus making distribution via a distributor unsuitable. Specifically, during pitch commands, the discharge port 221 and feed port 222 will no longer have the correct angular position relative to the stroke of the piston 24. Therefore, the hydraulic pump 20 is selected such that distribution is unaffected by the angular position of the body 22 (see in particular). Figure 4 ).

[0074] Preferably, the actuator 15 includes a dual-acting cylinder comprising a first chamber 151 and a second chamber 152 that are in sequential fluid communication with the discharge port 221 and the feed port 222. Therefore, actuation of the hydraulic pump 20 by the motor 29 has the effect of filling (or emptying) the first chamber 151 and emptying (or filling) the second chamber 152. Furthermore, the actuator 15 is rotatably fixed to and connected to the propeller 13, such that actuation of the actuator 15 (by sequentially filling and emptying the first and second chambers) has the effect of changing the pitch of the propeller 13.

[0075] exist Figure 4 In the variant embodiment shown, the cavity 224 of the body 22 is filled with hydraulic fluid, thus enabling the cavity to be used as a hydraulic fluid reservoir. Where applicable, hydraulic fluid is supplied to the cavity 224 through the hydraulic fluid reservoir 16.

[0076] The cylindrical section 23 is immersed in hydraulic fluid contained in the cavity 224.

[0077] In this variant embodiment, the cylinder includes a feed port 242 and a discharge port 232, the feed port being configured to receive hydraulic fluid from a cavity 224, and the discharge port being configured to pass through an annular groove 223 formed in the body 22. Figure 5 The hydraulic fluid contained in the cylinder is discharged to the propeller actuator 15. Therefore, in this variant embodiment, the annular groove 223 uses two ports (inlet and outlet) that are typically used to connect the cylinder of piston 24 to actuator 15 instead of the distribution plate.

[0078] The use of this annular groove 223, which is in fluid communication with the discharge port of the cylinder, enables the pump to operate regardless of the angular position of the body 22 and thus the angular position of the discharge port during piston 24 movement.

[0079] In an embodiment, each cylinder includes a device in the form of a drain valve 231 mounted at a drain port 232. Each drain valve 231 has an open configuration and a closed configuration. In the open configuration, the drain valve 231 opens and allows hydraulic fluid to flow from the cylinder to the annular groove 223. In the closed configuration, the drain valve 231 closes the cylinder and prevents hydraulic fluid from flowing between the cylinder and the annular groove 223. In the closed configuration, the drain valve 231 is thus able to prevent pressurized hydraulic fluid from the annular groove 223 from returning along the cylinder direction. Since the body 22 is rotatable, preferably, the drain valve 231 is mounted inside the cylinder, and the drain valve automatically (passively) positions itself in the open or closed configuration depending on the position of the piston 24 in the cylinder.

[0080] Similarly, each cylinder includes a device 241 configured to control the flow of hydraulic fluid between the cylinder and the barrel. In an embodiment, this device 241 includes a feed valve 241 mounted at a feed port 242. Each feed valve 241 has an open configuration and a closed configuration. In the open configuration, the feed valve 241 opens and allows hydraulic fluid to flow from the barrel to the cylinder. In the closed configuration, the discharge valve 241 closes the cylinder and prevents hydraulic fluid from flowing between the cylinder and the barrel. In the closed configuration, the feed valve 241 thus prevents pressurized hydraulic fluid from the cylinder from returning along the barrel direction. Since the barrel is rotatable, preferably, the feed valve 241 is mounted inside the cylinder, and the feed valve automatically (passively) positions itself in the open or closed configuration depending on the position of the piston 24 in the cylinder. Where applicable, in particular, the feed valve 241 may be mounted close to the sliding pad 25.

[0081] Regardless of the angular position of the pump body 22, the pump described above is functional. Because the pump is irreversible due to the configuration of the discharge and feed ports, the hydraulic actuator 11 may also include a hydraulic flow switching valve 14, which is positioned in the hydraulic circuit between the annular groove 223 and the actuator 15. Specifically, the hydraulic flow switching valve 14 is configured to selectively connect one or more chambers of the actuator 15 to the annular groove 223 and the cavity 224 according to the actuation requirements of the actuator 15 to obtain the desired propeller pitch.

[0082] The hydraulic flow switching valve 14 is controlled by the controller of the pitch changing mechanism to prevent the annular groove 223 from fluidly communicating with the first or second chamber 152 of the actuator 15, depending on the direction in which the propeller pitch must be changed. When the propeller pitch must be changed, the controller commands the motor to rotate the actuation shaft 21, thereby rotatably driving the cylinder 23 (or, where applicable, the disc 26). The rotation of the cylinder 23 (or, where applicable, the disc 26) has the effect of rotating the piston 24 about the axis of rotation of the drive shaft. Because the sliding pad of the piston 24 is in constant contact with the inclined disc, the rotation of the actuation shaft 21 causes the piston 24 to move axially within the corresponding cylinder of the piston, enabling the introduction and discharge of hydraulic fluid. Specifically, when one piston in piston 24 enters the feed configuration (in which the feed valve of that piston is open and the discharge valve of that piston is closed, allowing hydraulic fluid to enter the cylinder), the other piston in piston 24 enters the discharge configuration (in which the feed valve of that piston is closed and the discharge valve of that piston is open, allowing hydraulic fluid to exit the cylinder's discharge port 232 towards the annular groove 223), and vice versa. Thus, piston 24 continuously discharges pressurized hydraulic fluid into the annular groove 223. This pressurized hydraulic fluid is then conveyed from the annular groove 223 to the flow switching valve 14, which, depending on its position (defined by the controller and the propeller pitch command), delivers the pressurized hydraulic fluid to one or the other chamber of actuator 15. Therefore, the change in pitch caused by the rotational drive of actuator shaft 21 can be measured to determine the torque control of motor 29, enabling the acquisition of the desired pitch.

[0083] Typically, the pitch changing mechanism may also include a feathering system that operates without hydraulic fluid pressure. In an embodiment, the feathering system includes a lightweight type of counterweight.

[0084] When the hydraulic pump used in the pitch changing mechanism is irreversible, the pitch changing mechanism may also include a flow switching valve 14, which is configured to selectively fluidly communicate the hydraulic pump 20 with either the first chamber 151 or the second chamber 152 of the actuator 15, thereby enabling the change of the propeller pitch (see, for example, [reference needed]). Figure 7 ).

[0085] However, since each chamber in the actuator can be connected to one of the outlets of the hydraulic pump, it is not necessary to use such a flow switching valve when using a reversible hydraulic pump.

[0086] Therefore, this configuration of the pitch changing mechanism eliminates the need for an oil transfer bearing (OTB), thereby eliminating the risk of leakage, the associated return oil pump, and the excessive size of the associated oil tank. Furthermore, this circuit is independent of the lubrication unit. In particular, the pressure transmitted by the hydraulic pump 20 can reach a significant level (approximately 300 bar), which simplifies the size of the actuator 15.

Claims

1. A pitch changing mechanism for a propeller (13) of a turbine, the turbine comprising a stator and a rotor, the pitch changing mechanism comprising an electro-hydraulic actuator (11), the pitch changing mechanism comprising: - Motor (29), which is configured to be fixedly mounted on the stator portion of the turbine and includes an actuation shaft (21) capable of rotating about a rotation axis (A). - An axial piston hydraulic pump (20), the axial piston hydraulic pump being adapted to pressurize hydraulic fluid, the axial piston hydraulic pump (20) comprising: - Body (22), which is configured to be driven by the propeller (13); - A cylindrical section (23) housing a set of pistons (24) circumferentially distributed around the axis of rotation (A), each piston (24) including a sliding pad; and - Inclined disk (26), the inclined disk being inclined relative to the axis of rotation (A), each sliding pad (25) being supported on the inclined disk (26), One of the swash plate and the cylinder (23) is configured to be fixedly connected to the stator portion of the turbine to prevent the swash plate and the cylinder from rotating about the actuation shaft (21), and the other of the swash plate (26) and the cylinder (23) is rotatably fixed to the actuation shaft (21).

2. The pitch changing mechanism according to claim 1, wherein, The motor (29) is an asynchronous motor.

3. The pitch changing mechanism according to claim 1, wherein, The swash plate (26) is configured to be fixedly connected to the stator portion of the turbine, and the pitch changing mechanism further includes a first bearing (27a) configured to support the actuation shaft (21) and a second bearing (27b) configured to support the swash plate (26).

4. The pitch changing mechanism according to claim 3, wherein, The first bearing (27a) is installed between the actuation shaft (21) and the tilting disk (26).

5. The pitch changing mechanism according to claim 3, wherein, The second bearing (27b) is installed between the tilting plate (26) and the body (22).

6. The pitch changing mechanism according to claim 3, wherein, The swashplate (26) includes a first portion (26a) and a second portion (26b), the first portion including a surface inclined relative to the axis of rotation (A), the sliding pad (25) being supported on the surface, and the second portion being configured to be attached to the stator portion of the turbine.

7. The pitch changing mechanism according to claim 1, wherein, The cylinder (23) is configured to be fixedly connected to the stator portion of the turbine, and the pitch changing mechanism further includes a first bearing (27c) configured to support the swashplate (26) and a second bearing (27d) configured to support the cylinder (23).

8. The pitch changing mechanism according to claim 7, wherein, The first bearing (27c) is installed between the tilting plate (26) and the cylindrical portion (23).

9. The pitch changing mechanism according to claim 7, wherein, The second bearing (27d) is installed between the cylindrical portion (23) and the main body (22).

10. The pitch changing mechanism according to claim 1, wherein, The turbine also includes a planetary mechanical reducer (50) comprising a sun gear (51), a ring gear (52), and a planetary gear train (53), the ring gear being coaxial with the sun gear (51) and configured to rotatably drive the propeller, the planetary gear train being circumferentially distributed between the sun gear (51) and the ring gear (52) around the axis of rotation of the planetary mechanical reducer (50), each planetary gear being mounted on a planet carrier (54) fixed relative to the stator portion of the turbine, and elements in the swashplate (26) and the cylinder (23) configured to be fixedly connected to the stator portion of the turbine being mounted on the planet carrier (54).

11. The pitch changing mechanism according to claim 1, wherein, The pitch of the propeller (13) is configured to be controlled by the torque control of the motor (29).

12. The pitch changing mechanism according to claim 1 further includes a hydraulic fluid reservoir (16) configured to be rotatably fixed to the propeller.

13. The pitch changing mechanism of the propeller (13) according to claim 1, wherein, The main body (22) defines a cavity (224) filled with hydraulic fluid, and the pitch changing mechanism further includes: - A cylindrical portion (23), which is housed in the cavity (224) of the body to be immersed in the hydraulic fluid; - A set of cylinders formed inside the cylindrical portion (23), each cylinder housing a piston (24) capable of translational movement within the cylinder and including a feed port (242) and a discharge port (232), the feed port being configured to receive hydraulic fluid from the cavity (224), and the discharge port being configured to deliver the hydraulic fluid to the actuator of the propeller; and - An annular groove (223), which is formed in the body (22) and is in fluid communication with the discharge hole (232).

14. The pitch changing mechanism according to claim 13, wherein, Each cylinder also includes a discharge valve (231) mounted on the discharge port (232) and configured to prevent hydraulic fluid from flowing toward the cylinder through the annular groove (223).

15. The pitch changing mechanism according to claim 14, wherein, The discharge valve (231) is installed in the cylinder.

16. The pitch changing mechanism according to claim 13, wherein, Each cylinder also includes a feed valve (241) mounted on the feed port (242) and configured to prevent hydraulic fluid from flowing into the cavity (224).

17. The pitch changing mechanism according to claim 16, wherein, The feed valve (241) is mounted close to the sliding pad.

18. The pitch changing mechanism according to claim 16, wherein, The feed valve (241) is installed in the cylinder.

19. The pitch changing mechanism according to claim 13, wherein, The propeller actuator (15) includes two chambers, and the pitch changing mechanism also includes a hydraulic valve (14) configured to selectively connect one of the chambers of the actuator to the annular groove (223).

20. A turbine comprising a propeller (13) and a pitch changing mechanism according to any one of claims 1 to 19, the pitch changing mechanism being configured to actuate an actuator (15) mechanically connected to the propeller (13).

21. An aircraft comprising at least one turbine according to claim 20, the turbine being connected to the aircraft via a pylon.

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